The Effect of Graphite Venting on ISV Processing of Low Permeability Soils

In situ vitrification (ISV) is a promising technology for remediating buried waste and contaminated soil sites. Concerns exist, however, that low soil permeabilities may limit vapor transport away from the advancing ISV melt front, causing a melt expulsion that breaches ISV containment. A potential solution may be the use of a graphite rod placed vertically through the area being processed, which acts as a “preferred pathway” in venting generated vapors through the ISV melt. To evaluate this engineering solution, two ISV lab tests were conducted at the Idaho National Engineering Laboratory, using a low permeability clay material. One of the tests used the graphite rod concept, while the other did not. Test results found that the graphite rod is effective in preventing the buildup of pressures beneath the ISV melt. The graphite rod may also limit the amount of entrained particulate released to the offgas system during ISV processing.